Abacus



FIG. 1 is a perspective view of an abacus showing our new design in a first position.

FIG. 2 is a op plan view in a second position.

FIG. 3 is a front side elevation view of FIG. 1.

FIG. 4 is a front side elevation view in a third position; and,

FIG. 5 is a side plan view thereof. 

CLAIM The ornamental design for an abacus, as shown and described. 